<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        /* 类选择器 */
     .tou {
         color: red;
     }
     /* id选择器 */
     #big {  
         color: pink;
     }
    </style>
</head>
<body>
    <div class="tou">熊大</div>
    <div id="big">熊二</div>
    <div>光头强</div>
</body>
</html>